This loop of GOES-8 Sounder 7.0 micrometer InfraRed (water vapor) imagery shows the rapid eastward propagation of a shortwave across Nebraska, Iowa, and the southern Great Lakes region. Note the area of warming brightness temperatures (orange enhancement) in the wake of the departing shortwave -- this warming signaled a region of mesoscale subsidence and drying within the lower to middle troposphere, which moved east-southeastward across southern Minnesota and southern Wisconsin during the afternoon hours on 29 March 1999.